LANGUAGE INDEPENDENT ROBUST SKEW DETECTION AND CORRECTION TECHNIQUE FOR DOCUMENT IMAGES

Document image processing is an increasingly important technology essential in all optical character recognition (OCR) systems and for automation of various office documents. A document originally has zero-skew (tilt), but when a page is scanned or photo copied, skew may be introduced due to various factors and is practically unavoidable. Presence even a small amount of skew (0.50) will have detrimental effects on document analysis as it has a direct effect on the reliability and efficiency of segmentation, recognition and feature extraction stages. Therefore removal of skew is of paramount importance in the field of document analysis and OCR and is the first step to be accomplished. This paper presents a novel technique for skew detection and correction which is both language and content independent. The proposed technique is based on the maximum density of the foreground pixels and their orientation in the document image. Unlike other conventional algorithms which work only for machine printed textual documents scripted in English, this technique works well for all kinds of document images (machine printed, hand written, complex, noisy and simple). The technique presented here is tested with 150 different document image samples and is found to provide results with an accuracy of 0.1

Invoice Analysis Using Computer Vision

V posledních letech díky rozvoji algoritmů z oblasti počítačového vidění a strojového učení se těší velké oblibě i optické rozpoznání znaků a digitalizace tištěných textů. Touto problematikou se také zabývá tato práce. Cílem této práce je vytvoření programu, který automaticky detekuje základní informace z faktury a umožní s nimi dále pracovat (např. export do různých formátů).Recently optical character recognition and digitalization of printed text is becoming more populár thanks to development of computer vision algorithms. This work is also focused on this topic. Goal of this work is to create a program, which automatically detects basic invoice information and allows the user to proces them furthermore (for example export to various formats).460 - Katedra informatikyvýborn

Document Skew Detection and Correction Algorithm using Wavelet and Radon Transforms

Abstract:As part of research into document image processing, an algorithm has been developed to detect and correct the degree of skew in a scanned image. The principal components of the algorithm are the wavelet and radon transforms. The wavelet transform is used as a form of down-sampling process to reduce the amount of data to be processed. The performance of the algorithm has been evaluated using a sample size of several images taken from different types of document. Evaluation shows that a skew angle may be detected and corrected

An Image Analysis Method to Measure Cross-Sectional Tracheid Dimensions on Softwood Increment Cores

Anatomical properties of wood affect the properties of wood products. In this paper, an automated image analysis method for measuring cross-sectional tracheid dimensions of softwood cores is presented. The images used were single slice, confocal reflected light microscope images. By the use of the proposed method, automatic measurements of radial and tangential lumen diameter, as well as radial cell-wall thickness, of almost all individual tracheids are obtainable

RECOGNITION OF PRINTED KANNADA NUMERALS BY NEAREST NEIGHBOR METHOD

Numeral recognition is considered to be very prominent in most of the Character recognition researches. With respect to applications like number plate recognition and document processing the numerals are composed as a part of number plate images/application form type document images. This paper mainly focuses on eliminating language barriers that may arise while comprehending the regional language numerals by a non-regional user at the time of number plate recognition or other application form type document processing with special reference to Karnataka state. An algorithm is devised by incorporating the capabilities of functionalities of features the handwritten and printed Kannada numerals

Word Extraction Associated with a Confidence Index for On-Line Handwritten Sentence Recognition

International audienceThis paper presents a word extraction approach based on the use of a confidence index to limit the total number of segmentation hypotheses in order to further extend our on-line sentence recognition system to perform on-the-fly recognition. Our initial word extraction task is based on the characterization of the gap between each couple of consecutive strokes from the on-line signal of the handwritten sentence. A confidence index is associated to the gap classification result in order to evaluate its reliability. A reconsideration process is then performed to create additional segmentation hypotheses to ensure the presence of the correct segmentation among the hypotheses. In this process, we control the total number of segmentation hypotheses to limit the complexity of the recognition process and thus the execution time. This approach is evaluated on a test set of 425 English sentences written by 17 writers, using different metrics to analyze the impact of the word extraction task on the whole sentence recognition system's performances. The word extraction task using the best reconsideration strategy achieves a 97.94% word extraction rate and a 84.85% word recognition rate which represents a 33.1% word error rate decrease relatively to the initial word extraction task (with no segmentation hypothesis reconsideration)

Recognition of characters in document images using morphological operation

In this paper, we deal with the problem of document image rectification from image captured by digital cameras. The improvement on the resolution of digital camera sensors has brought more and more applications for non-contact text capture. It is widely used as a form of data entry from some sort of original paper data source, documents, sales receipts or any number of printed records. It is crucial to the computerization of printed texts so that they can be electronically searched, stored more compactly, displayed on-line, and used in machine processes such as machine translation, text-to-speech and text mining. Unfortunately, perspective distortion in the resulting image makes it hard to properly identify the contents of the captured text using traditional optical character recognition (OCR) systems. In this work we propose a new technique; it is a system that provides a full alphanumeric recognition of printed or handwritten characters at electronic speed by simply scanning the form. Optical character recognition, usually abbreviated as OCR is the mechanical or electronic conversion of scanned images of handwritten, typewritten or printed text into machine-encoded text. OCR software detects and extracts each character in the text of a scanned image, and using the ASCII code set, which is the American Standard Code for Information Interchange, converts it into a computer recognizable character. Once each character has been converted, the whole document is saved as an editable text document with a highest accuracy rate of 99.5 per cent, although it is not always this accurate. The basic idea of Optical Character Recognition (OCR) is to classify optical patterns (often contained in a digital image) corresponding to alphanumeric or other characters

Ultra-fast basic geometrical transformations on linear image data structure

This paper presents a general, ultra-fast approach for geometrical image transformations, based on the usage of linear lookup hash tables. The new method is developed to fix distortions on document images as part of a real-time optical character recognition (OCR) system. The approach is generalized and uses linear image representation combined with pre-computed lookup tables. Backward mapping is used for generation of lookup tables, while forward mapping is presented as an alternative and more efficient mapping model for specific cases. Also, a theoretical space and time complexity analysis of the proposed method is provided. To achieve maximal computational performance, pointer arithmetic and highly-optimized low-level machine code implementations are provided, including the specialized implementations for horizontal mirror, vertical mirror, and 90° rotation. Also, a modified variant of the approach, based on auto-generated machine code is presented. Very high computational performances are achieved at the expense of memory usage. The performances from the perspective of time complexity are analyzed and compared with classical implementation, FPGA implementation, and other implementations of the image rotation. Numerical results are given for a set of different PC specifications to provide full insight into the implementation performances. The processing time for very large images are below 200 ms for backward mapping and below 100 ms for forward mapping for most machines, which is 30–60 times faster than the classical implementation, 5–20 times faster than the FPGA implementation, and up to 6 times faster than other implementations of image rotation. Original documents belonging to Nikola Tesla are used for visual demonstration of performance.</p